Stability

Vertical stability functions.

These work with ndarrays of profiles; use the axis keyword argument to specify the axis along which pressure varies. For example, the default, following the Matlab versions, is axis=0, meaning the pressure varies along the first dimension. Use axis=-1 if pressure varies along the last dimension–that is, along a row, as the column index increases, in the 2-D case.

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gsw.stability.IPV_vs_fNsquared_ratio(SA, CT, p, p_ref=0, axis=0)[source]

Calculates the ratio of the vertical gradient of potential density to the vertical gradient of locally-referenced potential density. This is also the ratio of the planetary Isopycnal Potential Vorticity (IPV) to f times N^2, hence the name for this variable, IPV_vs_fNsquared_ratio (see Eqn. (3.20.17) of IOC et al. (2010)).

Parameters:

SAarray-like: Absolute Salinity, g/kg
tarray-like: In-situ temperature (ITS-90), degrees C
parray-like: Sea pressure (absolute pressure minus 10.1325 dbar), dbar
p_reffloat: Reference pressure, dbar

Returns:

IPV_vs_fNsquared_ratioarray: The ratio of the vertical gradient of potential density referenced to p_ref, to the vertical gradient of locally-referenced potential density, dimensionless.
p_midarray: Pressure at midpoints of p, dbar. The array shape matches IPV_vs_fNsquared_ratio.

gsw.stability.Nsquared(SA, CT, p, lat=None, axis=0)[source]

Calculate the square of the buoyancy frequency.

Parameters:

SAarray-like: Absolute Salinity, g/kg
CTarray-like: Conservative Temperature (ITS-90), degrees C
parray-like: Sea pressure (absolute pressure minus 10.1325 dbar), dbar
latarray-like, 1-D, optional: Latitude, degrees.
axisint, optional: The dimension along which pressure increases.

Returns:

N2array: Buoyancy frequency-squared at pressure midpoints, 1/s^2. The shape along the pressure axis dimension is one less than that of the inputs. (Frequency N is in radians per second.)
p_midarray: Pressure at midpoints of p, dbar. The array shape matches N2.

gsw.stability.Turner_Rsubrho(SA, CT, p, axis=0)[source]

Calculate the Turner Angle and the Stability Ratio.

Parameters:

SAarray-like: Absolute Salinity, g/kg
CTarray-like: Conservative Temperature (ITS-90), degrees C
parray-like: Sea pressure (absolute pressure minus 10.1325 dbar), dbar
axisint, optional: The dimension along which pressure increases.

Returns:

Tuarray: Turner Angle at pressure midpoints, degrees. The shape along the pressure axis dimension is one less than that of the inputs.
Rsubrhoarray: Stability Ratio, dimensionless. The shape matches Tu.
p_midarray: Pressure at midpoints of p, dbar. The array shape matches Tu.